Process of forming hydrazine



June 7, 1955 H. H. SISLER ETAL PROCESS OF FORMING HYDRAZINE Filed Jan.17, 1950 -L n+ AU E0 "N"... M0 VY l "O OM a OTSN. 5" H |U,O+ MYN $TOMFill; MH E Mm m Mw N w UQHDO H EWW N GL Q 2 MW U L E m 0 W I wwu ALR 4mEHDH m a MMN+T UA M S C EU 0 H 2E .3 $1M WIQ b C B U w a c A o HW N13.}, C A n I.\ .::ii--iiiiiii!{I}- c n rnlllL HYDRAZINE AND AMMONIUMCHLORIDE HZN NH +2NH Cl AND UNREACTED CHLORAMINE AND AMMONIA (ALLANHYDROUS) IN VENTORS R E m ST 7 S w .M/ K HT /m YR WW 4 R w Am Q H w M.

United States Patent PROCESS OF FORMING HY DRAZINE Harry H. Sisler andRobert Mattair, Columbus, Ohio, assignors to The Ohio State UniversityResearch Foundation, Columbus, Ohio, a corporation of Ohio ApplicationJanuary 17, 1950, Serial No. 139,098

6 Claims. (Cl. 23-190) The invention disclosed in this applicationrelates to new methods for the preparation of hydrazine; andincidentally a new method for the preparation of the intermediateproduct chloramine.

This application is in part a continuation of our copending applicationSerial No. 110,072, filed August 13, 1949, now abandoned.

Heretofore, hydrazine has been prepared commercially only by the actionof a metal hypochlorite (such as sodium hypochlorite) upon aqueousammonia (or urea). This commercial synthesis is understood to involvefirst the formation of monochloramine by reaction of the sodiumhypochlorite and an aqueous ammonia or an aqueous urea solution; and thesubsequent reaction of additional quantities of ammonia still in thesolution with the monochloramine. Hydrazine has also been synthesizedexperimentally (1) by the reduction of compounds containing anitrogen-nitrogen linkage, (2) by the decomposition of ammonia, and (3)by miscellaneous methods, including other methods of oxidation ofammonia. The yields in processes consisting of the reduction ofcompounds containing a nitrogen-nitrogen linkage have been very low andin fact have been considered too low to warrant consideration astechnical processes. The decomposition of ammonia has been attempted bypyrolysis and by other methods but in such processes, the yields arevery small (corresponding in the best production to about 0.25% based onthe ammonia which had undergone decomposition). As stated above,hydrazine has been prepared commercially by the reaction of ammonia inaqueous solution with sodium hypochlorite. From such processes there isa good yield, but other oxidation procedures have yielded only verysmall quantities of hydrazine and such processes are not commercial.

In the oxidation of ammonia through sodium hypochlorite it is believedas "stated above, that there is first formed chloramine and sodiumhydroxide. The addition of excess ammonia forms hydrazine, sodiumchloride, and water. This reaction is a slow one and competes with athird reaction which converts the hydrazine by reaction with thechloramine into ammonium chloride (NHlCl) and nitrogen. This thirdreaction effectively cuts down yields of hydrazine.

It has furthermore been stated in the literature that alkali isnecessary in order to cause conversionof chloramine by ammonia intohydrazine- We have proved that this is not true. Also in all 'of theprior art attempts to obtain hydrazine by oxidation of ammonia so far aswe know, the ammonia has been used in aqueous solution or a reaction hasbeen involved which forms water, thus inevitably involving an aqueoussolution. As stated above, this is definitely true of the commercialprocess. If the hydrazine is obtained in aqueous solution, it must bedehydrated in order to obtain an anhydrous hydrazine. For manycommercial applications anhydrous hydrazine is desirable. Dehydration ofhydrazine is a diflicult and expensive-process. On the Patented June 7,1955 ice 2 other hand, if hydrazine is obtained from the synthesis as ananhydrous product, the dehydration step is ob viated.

We have found that by the use of substantially anhydrous ammonia andchlorine, hydrazine may be formed in substantial quantities by chemicalreaction of ammonia with chlorine itself to form chloramine and then toform hydrazine provided there is more than sufiicient ammonia present toconvert substantially all of the chlorine into ammonium chloride.Moreover, such hydrazine is anhydrous.

One of the objects of our invention is, therefore, a new and simpleprocess for the efiicient production of hydrazine.

A further object of our invention is a process for the preparation ofhydrazine by the direct chemical reaction of ammonia and chlorine.

Another object of our invention is the chemical reaction of anhydrouschlorine and anhydrous ammonia to synthesize an anhydrous hydrazine.

A feature of our invention is the utilization of pressure and heat toincrease the yields of hydrazine from the interaction of anhydrouschlorine and ammonia.

Further objects and features will be apparent from the subjoinedspecification and claims when considered in connection with the figureof the drawings which illustrates an embodiment of our novel process.

In the drawings:

The figure illustrates the reactions involved in an embodiment of ourinvention. The overall reaction is C12 4NH3 N2H4 ZNHlCl The reactionoccurs in two stages as follows:

( 1) Cl2+2NH3- NHzCl-l-NH4C1 (2) NH2Cl+NH4Cl+2NH3- N2H4+2NH4C1 Thereaction of Equation 1 is a fast and apparently quantitative reaction.Apparently no hydrazine formation occurs at this point under theconditions under which we worked, but the entire process may be speededup byoperating it under the influence of higher temperature and pressureto yield appreciable amounts of hydrazine in the vapor phase reaction.After the gaseous products of the first step are condensed to the liquid'state, hydrazine is formed as shown by the reaction of Equation 2. Thisreaction is a slower reaction. It runs in competition with sidereactions which produce nitrogen rather than hydrazine. Theconcentration of the chloramine in the liquid mixture in the trapsappears to affect greatly the yield of hydrazine. A very large moleratio of ammonia to chlorine in the liquid phase reaction has adefinitely great beneficial'eifect in increasing the yield of hydrazine.The use of an inert solvent (miscible withliquid ammonia under the givenconditions) to dilute the liquid mixture also has a beneficial effect inincreasing the yield of hydrazine.

The previously known reactions of chlorine with ainmonia are theproduction of monochloramine, dichloramine, and trichloramine (i. e.nitrogen trichloride), as well as the production of free nitrogen. DeLong (1811) by the action of chlorine on an aqueous solution of ammoniumchloride obtained nitrogen .trichloride as a yellow oily liquid whichwas violently explosive. He lost an eye and three fingers in theresearch. It may be presumed that heretofore workers have been deterredfrom research on the interaction of anhydrous ammonia and chlorinebecause of the expected vigor of the reaction and the dangers attendantupon the formation of nitrogen trichloride. We have found that if weprovide a large excess of ammonia we can avoid the formation of nitrogentrichloride. We have found that by the reaction of substantiallyanhydrous chloride with an excess of substantially anhydrous ammonia wecan obtain hydrazine in yields as high as 30% of theoretical based uponthe chlorine in the overall reaction. We believe that we can improvethis yield under more favorable conditions. The hydrazine which weproduce is anhydrous. We can bubble gaseous chlorine into liquid ammoniaand secure the desired reaction. We can dissolve chlorine in anon-aqueous solvent and add such solution to liquid ammonia or to anon-aqueous solution thereof. We can mix gaseous chlorine, nitrogen andammonia under pressures above atmospheric and at temperatures above roomtemperature (as for example up to 150 C. or higher) in a pressurizedchamber. After reaction the mixtures can in each case be led from thereaction chamber through a series of traps but such treatment is hardlynecessary where the reaction is in liquid ammonia. We can mix gaseouschlorine with an inert gas such as nitrogen and then bring these gasesinto contact with gaseous ammonia to form chloramine. The chloramine soformed can be fed into liquid ammonia to form hydrazine.

We have found that when we mix chlorine gas which has been diluted withnitrogen gas with a large excess of ammonia gas and the resultinggaseous mixture is condensed to the liquid state in traps and theresulting liquid is allowed to stand and then the excess of ammonia isallowed to evaporate, a solid mixture which contains hydrazine isobtained. We have further found that the larger the mole ratio ofammonia to chlorine within reasonable limits, the greater the yield ofhydrazine. Specifically we have found that with mole ratios of less than50 to 1, though hydrazine may be obtained, the yield is relativelysmall, but at mole ratios of the order of magnitude of 350 to 1, yieldsof hydrazine as high as 30% based on total chlorine supplied can beobtained. We have found that the efiect of the ammonia-chlorine ratio onthe yield of hydrazine is operative chiefly in the condensation trapsrather than in the gas reaction tube. In other words, the reaction inthe gas tube is not particularly sensitive to the ammonia-chlorine ratioas long as a suflicient excess of ammonia to avoid nitrogen trichlorideor dichloramine formation is present. The reaction in the trap, however,is very sensitive to this ratio.

The anhydrous hydrazine may be recovered from the reaction productsmixture by any one of several methods. The mixture may consist ofhydrazine and ammonium chloride. There may also be present unreactedammonia and monochloramine. Monochloramine will react with ammonia toproduce either ammonium chloride and nitrogen or hydrazine and ammoniumchloride. The wide separation in the boiling points of nitrogen (-195C.), ammonia (-33 C.) and hydrazine (113 C.) with ammonium chlorideremaining solid until about 350 C. makes separation either by ordinaryfractional distillation or by azeotropic distillation possible. Also inthe laboratory the unreacted ammonia and the nitrogen may be evaporatedat atmospheric pressure and at room temperature, the residue dissolvedin water and acidified and then reacted with an aldehyde to form ahydrazine derivative, and thus recovered. Any suitable acid may be used,but we have used, sulfuric acid because of its ready availability. Also,we have used benzaldehyde to form a derivative because of thecomparatively easy identification of benzalazine.

The finely divided ammonium chloride may, if desired, be removed fromthe vapor mechanically, preferably before evaporation of the ammonia, asfor example, by electrical precipitation beforethe gases leave thereaction outlet tubes.

We have found that the yield of hydrazine formed by the reaction ofammonia and chlorine can be improved by subjecting the ;mixture ofproducts to heat (up to about 150 C.) .and pressure in pressureequipment.

We have found that by passing the mixed products from the reaction ofgaseous chlorine with a large excess of ammonia through a glass woolplug, the ammonium chloride produced in reaction of Equation 1 can bealmost completely removed, leaving an anhydrous gaseous mixture ofammonia, chloramine and nitrogen. This mixture can be used as a sourceof dry chloramine either for the preparation of hydrazine or for avariety of other synthetic chemical reactions. Furthermore, we have beenable to absorb the chloramine in dry ether and thus to obtain a dryethereal solution of chloramine which contains only small concentrationsof ammonia.

We have further found that whenever dry chloramine from whatever sourcederived, is passed into a large excess of liquid ammonia and thesolution is allowed to stand, there Will be an efficient production of arelatively large quantity of hydrazine.

We prefer that the gaseous product of the reaction of chlorine andammonia from which solid ammonium chloride may have been removed or maynot, should not be cooled suddenly prior to the entry of this productinto the liquid ammonia. We have made observations which indicate thatthe cooling of this gaseous product (NH2Cl+NH3) may promote theformation of ammonium chloride and nitrogen rather than hydrazine. Thisis a yield-reducing reaction and decreases the production of hydrazine.Therefore, for this and other reasons, we prefer to introduce gaseousreaction products into the liquid ammonia as rapidly and with as littleprevious cooling thereof as may be possible.

As stated above, we can dissolve chlorine in a nonaqueous solvent andadd such solution to liquid ammonia or a non-aqueous solution thereof.We prefer, in such cases, to choose a solvent which is miscible withliquid ammonia under the conditions of the reaction and which is inertboth to the chlorine and the liquid ammonia. In such case, We preferthat the solution of chlorine in the inert solvent be mixed thoroughlywith the liquid ammonia and allowed to stand for a sufficient length oftime to allow the complete reaction of the chlorine with the ammonia.

This we have discovered that anhydrous hydrazine may be prepared bymixing elementary chlorine (substantially anhydrous and either gaseousor dissolved in an inert solvent such as carbon tetrachloride) witheither liquid or gaseous ammonia (also substantially anhydrous). Theyields of hydrazine based upon the chlorine used and the followingequation are, as stated above, substantial.

Following are examples of our invention:

Example I We bubbled gaseous chlorine (C12) (previously dried so as tobe anhydrous or as nearly so as possible) into a well stirred excess ofliquid ammonia (also anhydrous or as nearly so as possible). Thechlorine gas was added at temperatures between room temperature (25 C.)and its boiling (liquefying) point (about 34). The liquid ammonia was attemperatures between its boiling (liquefying) point (about 33 C.) andits freezing point (about 77 C.). Gases leaving the reaction vessel werepassed through a series of traps kept at temperatures between 33 C. and77 C. The hydrazine was recovered from the reaction vessel and the trapsas a mixture containing hydrazine, chloramine, ammonium chloride, andunreacted ammonia. The'synthesis of the hydrazine was proved by formingthe benzaldehyde derivative (benzalazine). We did this by letting theexcess ammonia evaporate, dissolving the residues in water, acidifyingwith 10% sulfuricacid, and adding benzaldehyde. The benzalazine waspurified by (1) treatment with sodium hydroxide solution to getridof anybenzoic acid which might have formed by air oxidation of benzaldehyde;(2.)

washing with water; (3) recrystallization from ethyl alcohol and watermixture; (4) washing with water; (5) drying in air. The identity of theproduct with be'nzalazine was proved by (l) melting point; (2) mixedmelting point with an equal amount of known pure benzalazine.

Example II We dissolved chlorine in carbon tetrachloride (CCli), using4.6 grams of chlorine to 55 grams of the solvent. We added this solutiondropwise into 200 mlof liquid ammonia (NI-I3) with good stirring. Thetemperature of the liquid ammonia was maintained between its boilingpoint and its freezing point. Both the solution of chlorine in carbontetrachloride and the liquid ammonia were as nearly anhydrous aspossible. There was an excess of liquid ammonia over that required bythe equations:

The temperature of the solution of chlorine was maintained in a rangefrom room temperature (25 C.) to the freezing point of the solution. Theconcentration of'the solution was about 5 g. chlorine in 60 grams ofsolution. Gases leaving the reaction vessel were passed through a seriesof cooled traps kept at temperatures between 33 C. and -77 C. Thehydrazine was recovered from the reaction vessel and the traps in amixture containing hydrazine and ammonium chloride. The formation of thehydrazine was proved by forming the benzaldehyde derivative,benzalazine, by letting the excess ammonia evaporate, adding water tothe residues, separating oil? the carbon tetrachloride, extracting ittwice with dilute sulfuric acid, adding these water extracts to theother Water layer, acidifying this water solution with dilute sulfuricacid, and adding benzaldehyde. The benzalazine was purified andidentified in the same manner as explained in Example I.

Eaxrhple III We obtained gaseous chlorine as nearlyanhydrous aspossible. We mixed the chlorine with nitrogen (mole ratio N2 to C12equals 17 to 1) also as nearly anhydrous as possible, and then broughtthis mixture into contact with gaseous ammonia (also as nearly anhydrousas possible) (mole ratio NH: to C12 equals 267 to. 1). This mole ratioof ammonia to chlorine of 267 to '1 provided The gases leaving thereaction tube were led through a series of traps kept at temperaturesbetween --33 C. and 77 C. The incoming gases were passed from tanksthrough drying agents, and into the reaction tube. The flow of incominggases was continuous, so that there was a continuous stream of gases inthe reaction tube, fresh gases coming in at one end forcing the productsof the reaction through the other end and through the traps. The end ofthe last trap was open to the atmosphere. The condensate from the trapswas a mixture containing hydrazine, ammonia chloramine, and ammoniumchloride. In order to prove the synthesis of hydrazine the mixture wastreated by letting the mixture stand for from 12 to 16 hours at from 33C. to 77 C., then allowing the excess ammonia to evaporate, addingwater, acidifying, and adding benzaldehyde. The resulting benzalazinewas purified and its identity shown as in Example I. We obtained a yieldof about 30% of theoretical.

6 Example IV We conducted the reaction of gaseous chlorinewith gaseousammonia as described in Example III. Then we combined the contents ofall the traps. The combined condensate contained hydrazine, ammoniumchlo ride, monochloramine, and unreacted ammonia. We poured equalamounts into two similar tubes, A and B. After it had stood overnight at33 to 77, we allowed the excess ammonia to evaporate from tube A andthen recovered the hydrazine as benzalazine, purifying and identifyingit as in Example I. We subjected the contents of tube B to heat (up to150 C.) and pressure, in pressure equipment, then we cooled to liquidammonia temperature, let the excess ammonia evaporate,recoveredhydrazine as benzalazine, purified and identified it as inExample I. The yield of henzalazine, and therefore of hydrazine, wasabout three times better from tube B than from tube A.

Example V Anhydrous chlorine vapor, diluted with anhydrous nitrogen, wasmixed with anhydrous ammonia vapor and the reaction gas mixture,containing solid, finely divided ammonium chloride was then passedthrough glass wool plugs that strained substantially all of the ammoniumchloride out of the gas mixture. The reaction mixture was then condensedin a series of cooled traps. The molar ratio of ammonia to chlorine was81 to l. The yield of hydrazine, recovered as benzalazine, was 5.8% fromthe first trap. 'The second and third traps had been previously filledwith liquid ammonia to such an extent that any gases passing throughthem had to bubble through the liquid ammonia. The combined yield fromthese traps (second and third) was 7.8%. Total yield 13.6%. 53.4% of thechlorine used was recovered from the reaction tube and glass wool, byanalysis.

Example VI In another run, designed to be similar to the Example V inall respects, except that in this second run a certain amount of liquidammonia was placed in the first trap prior to the running of thereaction, the following data were obtained:

Anhydrous chloride vapor, diluted with the same amount of anhydrousnitrogen as in Example V was mixed with anhydrous ammonia vapor and thereaction mixture then passed through glass wool plugs that strainedsubstantially all of the finely divided ammonium chloride out of the gasmixture. The ratio of ammonia to chlorine in the vapor phase reactionwas 85 to l. The reaction mixture was then condensed in a series ofcooled traps. Prior to the reaction, there had been placed in the firsttrap an amount of liquid ammonia such that the total ratio of ammonia tochlorine, counting both the liquid and gaseous ammonia which was latercondensed to liquid ammonia, was 365 to l. The yield of hydrazine,recovered as benzalazine, from the first trap, was 23.7%. The second andthird traps had been filled with liquid ammonia, just as in run ExampleV. The combined yield from the second and third traps was 8.9%. Totalyield: 32.7%. 53.0% of the chlorine was recovered from the reaction tubeand glass wool, by analysis. Since the condition of the two runs, theamounts of ammonia, nitrogen and chlorine used, were carefullycontrolled in order that they be as alike as possible, within the limitsof experimental control, with the exception that extra ammonia wasprovided in the first trap, the results indicate that the difierence inyields can be attributed directly to the dilference in the molar ratiosof ammonia to chlorine in the two runs, in the liquid phase.

It is to be understood that the above described embodiments of ourinvention are for the purpose of illustration only and various changesmay be made therein without departing from the spirit and scope of ourinvention.

We claim:

1. A process of ,preparing substantially anhydrous hydrazine insolution'in liquid ammonia Which'consists of the combination of steps,of first introduciugsubstantially anhydrous gaseous chlorine intosubstantially anhydrous gaseous ammonia in a ratio-providing asubstantial excess over 2 moles of ammonia to each mole of chlorine toform substantially anhydrous gaseous chloramine and then contacting-thesubstantially anhydrous chloramine thus formed with a-large excess overtwo additional moles of substantially anhydrous liquid ammonia for eachmole ofchloramine to obtain substanliquid ammonia to form substantiallyanhydrous hydrazine in solution in liquid ammonia.

3. A process of preparing substantially anhydrous hydrazine in solutionin liquid ammonia which consists of the combination of steps of firstintroducingsubstantially anhydrous gaseous chlorine diluted with aninert gas into substantially anhydrous gaseous ammonia in aratioproviding substantially more than two moles of ammonia to each mole ofchlorine toformsubstan- -tially anhydrous chloramine and .thencontacting the substantially anhydrous chloramine soformed with a largeexcess over two additional moles of liquid ammonia for each mole ofchloramine to obtain substantially anhydrous hydrazine in solution inliquid ammonia.

4. A process of preparing substantially anhydrous hydrazine in solutionin liquid ammonia which consists of introducing substantially vanhydrousgaseous chlorine diluted with an inert gas into substantially anhydrousgaseous ammoniain a ratio providing a large excess over 4 moles ofammonia to each mole of chlorine to form substantiallytanhydrouschloramine andthencondensing the unreacted ammonia and contactingtheanhydrous chloramine thus formed with the condensed units .of thesubstantially anhydrous ammonia to form sub- 8 stantially anhydroushydrazine in solution in liquid ammonia.

5. A process for preparing anhydrous hydrazine comprising the steps offirst introducing anhydrous gaseous chlorine into anhydrous gaseousammonia in a ratio providing a substantialexcessaover two moles ofammonia to .each moleof chlorine to form anhydrous gaseous chloramine,.and second condensing the resulting mixture of ammonia and chloramineand admixing the mixture with a large excess over two additional molesof anhydrous liquid ammoniafor each mole of chloramine to obtainanhydrous hydrazine in solution in said liquid ammonia.

6. The process of preparing anhydrous hydrazine in solution in i liquidammonia which comprises the steps of introducing anhydrous gaseouschlorine into an excess of anhydrous gaseous ammonia above two moles ofammonia per -mole of :chlorine; to form chloramine and admixing the;resulting chloramine-ammonia mixture with additional anhydrous liquidammoniasufficient to provide an excess of more: than two moles ofammonia per mole of chloramine, ,thereby converting the chloramine toanhydrous hydrazine in solution in the excess liquid ammonia.

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2. A PROCESS OF PREPARING SUBSTANTIALLY ANHYDROUS HYDRAZINE IN SOLUTIONIN LIQUID AMMONIA WHICH CONSISTS OF INTRODUCING SUBSTANTIALLY ANHYDROUSGASEOUS CHLORINE INTO A LARGE EXCESS OVER THE EQUIVALENT MOLAR QUANTITYOF SUBSTANTIALLY ANHYDROUS GASEOUS AMMONIA TO FORM SUBSTANTIALLYANHYDROUS CHLORAMINE AND THEN CONDENSING THE UNREACTED SUBSTANTIALLYANHYDROUS AMMONIA TO THE LIQUID STATE AND CONTACTING THE SUBSTANTIALLYANHYDROUS CHLORAMINE THUS FORMED WITH THE SUBSTANTIALLY ANHYDROUS LIQUIDAMMONIA TO FORM SUBSTANTIALLY ANHYDROUS HYDRAZINE IN SOLUTION IN LIQUIDAMMONIA.